I need some clarification on the magneto horn

[LittleTimmy52]

Edit: I doni deed have the early horn, there was only the 2 and 1 post variants, mine was modified to be used in a later setup, literally 2 rubber washers on one post fixed the issue. Idk why it is now a bit quieter but it works and is like everything else on the thing, good enough. Thanks for the reply.

I hear many things from people and I'm just trying to get the right horn or maybe the one I have is correct, I'm just not sure. My situation is, I have a magneto horn it has 2 contacts, one has continuity with the horns metal body the other is insulated from the body, the horn button grounds the horn to sound it, but it also grounds through the mounting bracket on the firewall which is grounding on the steering column bolt that holds one side in. I heard 2 things, there is one where both contacts are insulated and I heard that there's only 2 one with one contact and one with 2 like mine, so is it possible that my one uninsulated contract is supposed to be insulated or maybe something inside is shorting to the body? Again, I have a double contact mag horn but IT can be grounded via the contact or body for whatever reason. Any clarification would be appreciated.

[DanTreace]

Made this post a while back. Info from a knowledgeable T person who made reproductions of T horns.



Re: Magneto Horn Questions....
Post Sat Sep 18, 2021 3:08 pm

John Regan gave this explanation of the two versions of the magneto horns:

John F. Regan on Thursday, September 10, 2015 - 09:25 am:
Mag horns are wired 2 different ways. The early mag horns have both electrical connections isolated from the horn housing and thus isolated from ground. These are used on the 1915 to early 1917 or so. On those cars one connection of the mag horn is connected to the mag post of the motor and the other connection goes up the steering column to the horn button where it is grounded to complete the circuit and honk the horn. On late mag horns one of the connections is wired directly to ground internally and there is only a single outside power connection for the horn.

On the later cars a wire from the magneto goes up to the horn button and then the button completes the connection to another wire that goes down the column to the horn connection. Thus the horn button supplies a "hot" power connection to the horn. The mag horn housing MUST be grounded on these horns. During the transition years the magneto horns were supplied with 2 isolated connections but one of them had to be grounded when used on later cars. This grounding of one of the connections was accomplished by simply removing the outside hardware and insulation washer and then putting the hardware back in place without the insulating washer to thus ground the connection to the horn housing. The horn then had to be mounted with a good ground to its housing.

Thus you can make an early horn (with 2 connections) work on any T with a magneto and horn button but you cannot use the later magneto horn on the early T unless you go inside of it and remove the internal ground connection and then redrill the horn and bring out the previously grounded connection so that it can be grounded by the horn button as used on 15-early 17.

[LittleTimmy52]

Made this post a while back. Info from a knowledgeable T person who made reproductions of T horns.



Re: Magneto Horn Questions....
Post Sat Sep 18, 2021 3:08 pm

John Regan gave this explanation of the two versions of the magneto horns:

John F. Regan on Thursday, September 10, 2015 - 09:25 am:
Mag horns are wired 2 different ways. The early mag horns have both electrical connections isolated from the horn housing and thus isolated from ground. These are used on the 1915 to early 1917 or so. On those cars one connection of the mag horn is connected to the mag post of the motor and the other connection goes up the steering column to the horn button where it is grounded to complete the circuit and honk the horn. On late mag horns one of the connections is wired directly to ground internally and there is only a single outside power connection for the horn.

On the later cars a wire from the magneto goes up to the horn button and then the button completes the connection to another wire that goes down the column to the horn connection. Thus the horn button supplies a "hot" power connection to the horn. The mag horn housing MUST be grounded on these horns. During the transition years the magneto horns were supplied with 2 isolated connections but one of them had to be grounded when used on later cars. This grounding of one of the connections was accomplished by simply removing the outside hardware and insulation washer and then putting the hardware back in place without the insulating washer to thus ground the connection to the horn housing. The horn then had to be mounted with a good ground to its housing.

Thus you can make an early horn (with 2 connections) work on any T with a magneto and horn button but you cannot use the later magneto horn on the early T unless you go inside of it and remove the internal ground connection and then redrill the horn and bring out the previously grounded connection so that it can be grounded by the horn button as used on 15-early 17.

Thanks for the insight. The previous owner removed the 2 rubber washers and stuck it on a block mount to presumably use it on a later setup, putting 2 washers back on that post re isolated it and it works as intended just a bit quieter. Thank you again.